/* ----------------------------------------------------------------------
* Copyright (C) 2010-2014 ARM Limited. All rights reserved.
*
* $Date:        19. March 2015
* $Revision: 	V.1.4.5
*
* Project: 	    CMSIS DSP Library
* Title:		arm_conv_fast_opt_q15.c
*
* Description:	Fast Q15 Convolution.
*
* Target Processor: Cortex-M4/Cortex-M3
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*   - Redistributions of source code must retain the above copyright
*     notice, this list of conditions and the following disclaimer.
*   - Redistributions in binary form must reproduce the above copyright
*     notice, this list of conditions and the following disclaimer in
*     the documentation and/or other materials provided with the
*     distribution.
*   - Neither the name of ARM LIMITED nor the names of its contributors
*     may be used to endorse or promote products derived from this
*     software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
* -------------------------------------------------------------------- */

#include "arm_math.h"

/**
 * @ingroup groupFilters
 */

/**
 * @addtogroup Conv
 * @{
 */

/**
 * @brief Convolution of Q15 sequences (fast version) for Cortex-M3 and Cortex-M4.
 * @param[in] *pSrcA points to the first input sequence.
 * @param[in] srcALen length of the first input sequence.
 * @param[in] *pSrcB points to the second input sequence.
 * @param[in] srcBLen length of the second input sequence.
 * @param[out] *pDst points to the location where the output result is written.  Length srcALen+srcBLen-1.
 * @param[in]  *pScratch1 points to scratch buffer of size max(srcALen, srcBLen) + 2*min(srcALen, srcBLen) - 2.
 * @param[in]  *pScratch2 points to scratch buffer of size min(srcALen, srcBLen).
 * @return none.
 *
 * \par Restrictions
 *  If the silicon does not support unaligned memory access enable the macro UNALIGNED_SUPPORT_DISABLE
 *	In this case input, output, scratch1 and scratch2 buffers should be aligned by 32-bit
 *
 * <b>Scaling and Overflow Behavior:</b>
 *
 * \par
 * This fast version uses a 32-bit accumulator with 2.30 format.
 * The accumulator maintains full precision of the intermediate multiplication results
 * but provides only a single guard bit. There is no saturation on intermediate additions.
 * Thus, if the accumulator overflows it wraps around and distorts the result.
 * The input signals should be scaled down to avoid intermediate overflows.
 * Scale down the inputs by log2(min(srcALen, srcBLen)) (log2 is read as log to the base 2) times to avoid overflows,
 * as maximum of min(srcALen, srcBLen) number of additions are carried internally.
 * The 2.30 accumulator is right shifted by 15 bits and then saturated to 1.15 format to yield the final result.
 *
 * \par
 * See <code>arm_conv_q15()</code> for a slower implementation of this function which uses 64-bit accumulation to avoid wrap around distortion.
 */

void arm_conv_fast_opt_q15(
    q15_t *pSrcA,
    uint32_t srcALen,
    q15_t *pSrcB,
    uint32_t srcBLen,
    q15_t *pDst,
    q15_t *pScratch1,
    q15_t *pScratch2)
{
    q31_t acc0, acc1, acc2, acc3;                  /* Accumulators */
    q31_t x1, x2, x3;                              /* Temporary variables to hold state and coefficient values */
    q31_t y1, y2;                                  /* State variables */
    q15_t *pOut = pDst;                            /* output pointer */
    q15_t *pScr1 = pScratch1;                      /* Temporary pointer for scratch1 */
    q15_t *pScr2 = pScratch2;                      /* Temporary pointer for scratch1 */
    q15_t *pIn1;                                   /* inputA pointer */
    q15_t *pIn2;                                   /* inputB pointer */
    q15_t *px;                                     /* Intermediate inputA pointer  */
    q15_t *py;                                     /* Intermediate inputB pointer  */
    uint32_t j, k, blkCnt;                         /* loop counter */
    uint32_t tapCnt;                               /* loop count */
#ifdef UNALIGNED_SUPPORT_DISABLE

    q15_t a, b;

#endif	/*	#ifdef UNALIGNED_SUPPORT_DISABLE	*/

    /* The algorithm implementation is based on the lengths of the inputs. */
    /* srcB is always made to slide across srcA. */
    /* So srcBLen is always considered as shorter or equal to srcALen */
    if(srcALen >= srcBLen)
    {
        /* Initialization of inputA pointer */
        pIn1 = pSrcA;

        /* Initialization of inputB pointer */
        pIn2 = pSrcB;
    }
    else
    {
        /* Initialization of inputA pointer */
        pIn1 = pSrcB;

        /* Initialization of inputB pointer */
        pIn2 = pSrcA;

        /* srcBLen is always considered as shorter or equal to srcALen */
        j = srcBLen;
        srcBLen = srcALen;
        srcALen = j;
    }

    /* Pointer to take end of scratch2 buffer */
    pScr2 = pScratch2 + srcBLen - 1;

    /* points to smaller length sequence */
    px = pIn2;

    /* Apply loop unrolling and do 4 Copies simultaneously. */
    k = srcBLen >> 2u;

    /* First part of the processing with loop unrolling copies 4 data points at a time.
     ** a second loop below copies for the remaining 1 to 3 samples. */

    /* Copy smaller length input sequence in reverse order into second scratch buffer */
    while(k > 0u)
    {
        /* copy second buffer in reversal manner */
        *pScr2-- = *px++;
        *pScr2-- = *px++;
        *pScr2-- = *px++;
        *pScr2-- = *px++;

        /* Decrement the loop counter */
        k--;
    }

    /* If the count is not a multiple of 4, copy remaining samples here.
     ** No loop unrolling is used. */
    k = srcBLen % 0x4u;

    while(k > 0u)
    {
        /* copy second buffer in reversal manner for remaining samples */
        *pScr2-- = *px++;

        /* Decrement the loop counter */
        k--;
    }

    /* Initialze temporary scratch pointer */
    pScr1 = pScratch1;

    /* Assuming scratch1 buffer is aligned by 32-bit */
    /* Fill (srcBLen - 1u) zeros in scratch1 buffer */
    arm_fill_q15(0, pScr1, (srcBLen - 1u));

    /* Update temporary scratch pointer */
    pScr1 += (srcBLen - 1u);

    /* Copy bigger length sequence(srcALen) samples in scratch1 buffer */

#ifndef UNALIGNED_SUPPORT_DISABLE

    /* Copy (srcALen) samples in scratch buffer */
    arm_copy_q15(pIn1, pScr1, srcALen);

    /* Update pointers */
    pScr1 += srcALen;

#else

    /* Apply loop unrolling and do 4 Copies simultaneously. */
    k = srcALen >> 2u;

    /* First part of the processing with loop unrolling copies 4 data points at a time.
     ** a second loop below copies for the remaining 1 to 3 samples. */
    while(k > 0u)
    {
        /* copy second buffer in reversal manner */
        *pScr1++ = *pIn1++;
        *pScr1++ = *pIn1++;
        *pScr1++ = *pIn1++;
        *pScr1++ = *pIn1++;

        /* Decrement the loop counter */
        k--;
    }

    /* If the count is not a multiple of 4, copy remaining samples here.
     ** No loop unrolling is used. */
    k = srcALen % 0x4u;

    while(k > 0u)
    {
        /* copy second buffer in reversal manner for remaining samples */
        *pScr1++ = *pIn1++;

        /* Decrement the loop counter */
        k--;
    }

#endif	/*	#ifndef UNALIGNED_SUPPORT_DISABLE	*/


#ifndef UNALIGNED_SUPPORT_DISABLE

    /* Fill (srcBLen - 1u) zeros at end of scratch buffer */
    arm_fill_q15(0, pScr1, (srcBLen - 1u));

    /* Update pointer */
    pScr1 += (srcBLen - 1u);

#else

    /* Apply loop unrolling and do 4 Copies simultaneously. */
    k = (srcBLen - 1u) >> 2u;

    /* First part of the processing with loop unrolling copies 4 data points at a time.
     ** a second loop below copies for the remaining 1 to 3 samples. */
    while(k > 0u)
    {
        /* copy second buffer in reversal manner */
        *pScr1++ = 0;
        *pScr1++ = 0;
        *pScr1++ = 0;
        *pScr1++ = 0;

        /* Decrement the loop counter */
        k--;
    }

    /* If the count is not a multiple of 4, copy remaining samples here.
     ** No loop unrolling is used. */
    k = (srcBLen - 1u) % 0x4u;

    while(k > 0u)
    {
        /* copy second buffer in reversal manner for remaining samples */
        *pScr1++ = 0;

        /* Decrement the loop counter */
        k--;
    }

#endif	/*	#ifndef UNALIGNED_SUPPORT_DISABLE	*/

    /* Temporary pointer for scratch2 */
    py = pScratch2;


    /* Initialization of pIn2 pointer */
    pIn2 = py;

    /* First part of the processing with loop unrolling process 4 data points at a time.
     ** a second loop below process for the remaining 1 to 3 samples. */

    /* Actual convolution process starts here */
    blkCnt = (srcALen + srcBLen - 1u) >> 2;

    while(blkCnt > 0)
    {
        /* Initialze temporary scratch pointer as scratch1 */
        pScr1 = pScratch1;

        /* Clear Accumlators */
        acc0 = 0;
        acc1 = 0;
        acc2 = 0;
        acc3 = 0;

        /* Read two samples from scratch1 buffer */
        x1 = *__SIMD32(pScr1)++;

        /* Read next two samples from scratch1 buffer */
        x2 = *__SIMD32(pScr1)++;

        tapCnt = (srcBLen) >> 2u;

        while(tapCnt > 0u)
        {

#ifndef UNALIGNED_SUPPORT_DISABLE

            /* Read four samples from smaller buffer */
            y1 = _SIMD32_OFFSET(pIn2);
            y2 = _SIMD32_OFFSET(pIn2 + 2u);

            /* multiply and accumlate */
            acc0 = __SMLAD(x1, y1, acc0);
            acc2 = __SMLAD(x2, y1, acc2);

            /* pack input data */
#ifndef ARM_MATH_BIG_ENDIAN
            x3 = __PKHBT(x2, x1, 0);
#else
            x3 = __PKHBT(x1, x2, 0);
#endif

            /* multiply and accumlate */
            acc1 = __SMLADX(x3, y1, acc1);

            /* Read next two samples from scratch1 buffer */
            x1 = _SIMD32_OFFSET(pScr1);

            /* multiply and accumlate */
            acc0 = __SMLAD(x2, y2, acc0);
            acc2 = __SMLAD(x1, y2, acc2);

            /* pack input data */
#ifndef ARM_MATH_BIG_ENDIAN
            x3 = __PKHBT(x1, x2, 0);
#else
            x3 = __PKHBT(x2, x1, 0);
#endif

            acc3 = __SMLADX(x3, y1, acc3);
            acc1 = __SMLADX(x3, y2, acc1);

            x2 = _SIMD32_OFFSET(pScr1 + 2u);

#ifndef ARM_MATH_BIG_ENDIAN
            x3 = __PKHBT(x2, x1, 0);
#else
            x3 = __PKHBT(x1, x2, 0);
#endif

            acc3 = __SMLADX(x3, y2, acc3);

#else

            /* Read four samples from smaller buffer */
            a = *pIn2;
            b = *(pIn2 + 1);

#ifndef ARM_MATH_BIG_ENDIAN
            y1 = __PKHBT(a, b, 16);
#else
            y1 = __PKHBT(b, a, 16);
#endif

            a = *(pIn2 + 2);
            b = *(pIn2 + 3);
#ifndef ARM_MATH_BIG_ENDIAN
            y2 = __PKHBT(a, b, 16);
#else
            y2 = __PKHBT(b, a, 16);
#endif

            acc0 = __SMLAD(x1, y1, acc0);

            acc2 = __SMLAD(x2, y1, acc2);

#ifndef ARM_MATH_BIG_ENDIAN
            x3 = __PKHBT(x2, x1, 0);
#else
            x3 = __PKHBT(x1, x2, 0);
#endif

            acc1 = __SMLADX(x3, y1, acc1);

            a = *pScr1;
            b = *(pScr1 + 1);

#ifndef ARM_MATH_BIG_ENDIAN
            x1 = __PKHBT(a, b, 16);
#else
            x1 = __PKHBT(b, a, 16);
#endif

            acc0 = __SMLAD(x2, y2, acc0);

            acc2 = __SMLAD(x1, y2, acc2);

#ifndef ARM_MATH_BIG_ENDIAN
            x3 = __PKHBT(x1, x2, 0);
#else
            x3 = __PKHBT(x2, x1, 0);
#endif

            acc3 = __SMLADX(x3, y1, acc3);

            acc1 = __SMLADX(x3, y2, acc1);

            a = *(pScr1 + 2);
            b = *(pScr1 + 3);

#ifndef ARM_MATH_BIG_ENDIAN
            x2 = __PKHBT(a, b, 16);
#else
            x2 = __PKHBT(b, a, 16);
#endif

#ifndef ARM_MATH_BIG_ENDIAN
            x3 = __PKHBT(x2, x1, 0);
#else
            x3 = __PKHBT(x1, x2, 0);
#endif

            acc3 = __SMLADX(x3, y2, acc3);

#endif	/*	#ifndef UNALIGNED_SUPPORT_DISABLE	*/

            /* update scratch pointers */
            pIn2 += 4u;
            pScr1 += 4u;


            /* Decrement the loop counter */
            tapCnt--;
        }

        /* Update scratch pointer for remaining samples of smaller length sequence */
        pScr1 -= 4u;

        /* apply same above for remaining samples of smaller length sequence */
        tapCnt = (srcBLen) & 3u;

        while(tapCnt > 0u)
        {

            /* accumlate the results */
            acc0 += (*pScr1++ * *pIn2);
            acc1 += (*pScr1++ * *pIn2);
            acc2 += (*pScr1++ * *pIn2);
            acc3 += (*pScr1++ * *pIn2++);

            pScr1 -= 3u;

            /* Decrement the loop counter */
            tapCnt--;
        }

        blkCnt--;


        /* Store the results in the accumulators in the destination buffer. */

#ifndef ARM_MATH_BIG_ENDIAN

        *__SIMD32(pOut)++ =
            __PKHBT(__SSAT((acc0 >> 15), 16), __SSAT((acc1 >> 15), 16), 16);

        *__SIMD32(pOut)++ =
            __PKHBT(__SSAT((acc2 >> 15), 16), __SSAT((acc3 >> 15), 16), 16);


#else

        *__SIMD32(pOut)++ =
            __PKHBT(__SSAT((acc1 >> 15), 16), __SSAT((acc0 >> 15), 16), 16);

        *__SIMD32(pOut)++ =
            __PKHBT(__SSAT((acc3 >> 15), 16), __SSAT((acc2 >> 15), 16), 16);



#endif /*      #ifndef ARM_MATH_BIG_ENDIAN       */

        /* Initialization of inputB pointer */
        pIn2 = py;

        pScratch1 += 4u;

    }


    blkCnt = (srcALen + srcBLen - 1u) & 0x3;

    /* Calculate convolution for remaining samples of Bigger length sequence */
    while(blkCnt > 0)
    {
        /* Initialze temporary scratch pointer as scratch1 */
        pScr1 = pScratch1;

        /* Clear Accumlators */
        acc0 = 0;

        tapCnt = (srcBLen) >> 1u;

        while(tapCnt > 0u)
        {

            acc0 += (*pScr1++ * *pIn2++);
            acc0 += (*pScr1++ * *pIn2++);

            /* Decrement the loop counter */
            tapCnt--;
        }

        tapCnt = (srcBLen) & 1u;

        /* apply same above for remaining samples of smaller length sequence */
        while(tapCnt > 0u)
        {

            /* accumlate the results */
            acc0 += (*pScr1++ * *pIn2++);

            /* Decrement the loop counter */
            tapCnt--;
        }

        blkCnt--;

        /* The result is in 2.30 format.  Convert to 1.15 with saturation.
         ** Then store the output in the destination buffer. */
        *pOut++ = (q15_t) (__SSAT((acc0 >> 15), 16));

        /* Initialization of inputB pointer */
        pIn2 = py;

        pScratch1 += 1u;

    }

}

/**
 * @} end of Conv group
 */
